Justin (Lou Taylor Pucci, letting sincerity cut through his deadpan) is a teen still sucking his thumb. It infuriates him and confounds Mike (Vincent D’Onofrio) and Audrey (Tilda Swinton) — well-meaning parents with their own inferiority complexes, yearning for bygone youths they’ve idolized beyond their realities.

After Justin is diagnosed with ADD, prescription drugs sharpen his focus, but this flipped switch seems almost too simple — “It was almost easier when he was always fucking up,” Mike says — and his authority figures wrestle over whether it’s sacrificing what makes Justin Justin. (Swinton and D’Onofrio are both excellent, with D’Onofrio exhibiting never-before-seen vulnerability.)

Drifting between extremes isn’t always reason to sound the alarm. It could just be teen experimentation and experience — navigating a path to identity rather than resorting to biochemical ideals.

And Justin’s condition is only an awkward physical manifestation of how people cling to pasts as a security blanket. “Thumbsucker” doesn’t condone recklessly leaping, just the wisdom to never trick ourselves into thinking our current situation is the only answer.